1. Field of the Invention
This invention relates to a method and apparatus for detecting a moving object by detecting a change in an image of the object.
2. Description of the Related Art
Image processing techniques have been developed and used for a plurality of applications. One such application is for a monitoring apparatus which uses an image recognition technique. More specifically, such apparatus may be used to recognize a trespasser from an image taken by a TV camera.
A common technique for recognizing a trespasser is by using an image subtraction technique. That is, this technique (hereinafter referred to as an image subtraction technique) is characterized by using a TV camera to take two images at different times of an image area and subtracting the two images taken by the TV camera.
According to this technique, the subtracted image indicates a changing image such as may be caused by a moving object. The subtracted image can be analyzed so that the trespasser may be detected.
This image subtraction technique, however, has certain drawbacks. For example, the subtracted image includes the moving image corresponding to a moving object and a non-moving image corresponding to a fixed object or changing background conditions. This is partly due to the fact that background conditions and recording conditions vary. Recording conditions include weather, the position of the sun and the like. As these and other recording conditions vary, the image taken by the TV camera may vary even though there is no moving object in the image area. This may give rise to an erroneous indication of a moving object in the image area even though no moving object is present therein.